The Central Eastern Desert and Red Sea region have emerged as a significant area of interest for geothermal energy exploration, owing to their unique geological characteristics and active tectonic activity. This research aims to enhance our understanding of the region\'s geothermal potential through a comprehensive analysis of gravity and magnetic data. By utilizing a 3D gravity inversion model, a detailed examination of subsurface structures and density variations was conducted. Similarly, a 3D magnetic inversion model was employed to investigate subsurface magnetic properties. Integration result from the Pygimli library ensured robustness and accuracy in the inversion results. Furthermore, a temperature model was developed using the WINTERC-G model and inversion techniques, shedding light on the thermal structure and potential anomalies in the study area. The analysis of the Bouguer gravity map, 3D gravity inversion model, and magnetic data inversion yielded significant findings. The Red Sea exhibited higher gravity values compared to the onshore Eastern Desert, attributed to the presence of a thinner and denser oceanic crust as opposed to the less dense continental crust in the Eastern Desert. The 3D gravity inversion model revealed distinct variations in density, particularly high-density zones near the surface of the Red Sea, indicating underlying geological structures and processes. Conversely, density gradually decreased with depth along the onshore line, potentially influenced by a higher concentration of crustal fractures. The magnetic data inversion technique provided additional insights, highlighting areas with demagnetized materials, indicative of elevated temperatures. These findings were consistent with the correlation between high-density areas and low magnetic susceptibility values, reinforcing the proposition of increased heat transfer from the Red Sea. Comparative analysis of temperature profiles further confirmed the presence of elevated temperatures in promising zones, emphasizing the geothermal potential associated with heat transfer from the Red Sea.This research contributes to the understanding of the geothermal resources in the Central Eastern Desert and Red Sea region. The results from gravity and magnetic data inversions, combined with temperature profiles, provide valuable information for future geothermal exploration and utilization efforts. The findings underscore the importance of geothermal energy in achieving sustainability and contribute to the global discourse on renewable energy sources.

Many cities worldwide lay upon alluvial aquifers which have a great potential for low temperature geothermal installations thanks to the thermal diffusive properties of saturated porous media and the constant temperature of the subsurface. In addition, aquifers with fast moving groundwater have a higher potential due to the additional energy replenishment by advection, which is often underestimated. This work aims at bridging the gap between quantitative hydro-thermal numerical analysis and regional scale assessment developing a process-based surrogate model for the estimation of the thermal exchange (geothermal) potential of ground source heat pumps (GSHP) considering groundwater advection. The proposed method is based on a synthetic 3D FEM model reproducing the infinite line source configuration and introducing groundwater advection. Conductive/advective g-functions were derived from the numerically simulated space-time thermal perturbation for a comprehensive set of hydrogeological regimes, and a surrogate model was developed by a machine learning (ML) regression of the thermal response of the system. This solution, beyond the run time of the numerical study and the ML training phase, is very fast, applicable at any scale and scalable to any desired depth. The trained model can be used to predict the geothermal potential of GSHP for almost all sedimentary basins around the world upon the availability of the required input data (aquifer thickness and saturation, aquifer porosity and groundwater flow velocity). In this study, large scale geothermal potential maps were generated from input layers implemented in a GIS, for a demonstrative area in northern Italy showing highly variable groundwater flow (Darcy velocity from 10-3 to 10+3 m/y). A promising increase (up to +250 %) in the thermal exchange potential of GSHP due to the contribution of advection was highlighted discussing the benefits of groundwater flow and the amount of usable potential with implications on shallow geothermal energy management and development.

The world has capitalized on numerous renewable energy resources by developing its energy infrastructure mainly around solar, biomass, and hydro energy. However, geothermal energy has not yet been developed at a significant scale, despite reports from 62 wells showing evidence of geothermal gradients ranging from 20.8 °C/km to 48.7 °C/km in various areas of the world. Recent studies suggest that Bangladesh also has a huge potential for geothermal energy. This review extensively reports on exploiting the range of geothermal temperature in various direct and indirect energy application sectors including but not limited to the agriculture and industrial sector of Bangladesh. Additionally, the authors have analyzed and proposed adaptable measures to harness the abundance of geothermal energy. Furthermore, a comparative and possible solution has been discussed extensively for implementing a geothermal powerplant by analyzing techno-economic costs, policies, and systems of other countries in the world. Further, this review also shows the prospect of geothermal energy for Bangladesh as a case study.

While urban underground is being increasingly used for various purposes, two concerns should be addressed with respect to the urban underground climate change: i) how much energy has been stored in urban subsurface due to the heat rejection from underground heated spaces (such as tunnels and basements) and ii) how much of the thermal demand of a city or district can be supplied by harvesting this accumulative thermal energy in the ground. However, our understanding of the temperature rise in the ground and of the geothermal potential of urban subsurface is still limited. This paper quantifies the geothermal potential for a 12 km2 densely populated borough in central London by considering the spatio-temporal temperature variation in the ground owing to continuous rejection of heat into the ground, coupled with the effect of geothermal extraction capacity. A large-scale transient semi-3D geothermal subsurface model of the site is developed, and the thermal interaction between underground heated spaces, geothermal energy extraction systems and the ground and groundwater are simulated. The concurrent heat rejection and extraction processes in the subsurface are computed so that the most influencing parameters of the subsurface on its geothermal potential are identified. Results show that up to 50% of the borough\'s total heat demand can be supplied via geothermal installations leading to around 33% reduction in CO2 emission. The geothermal extraction efficiency in sand and gravel primarily depends on the ground conditions such as the thickness of the permeable layer and the groundwater flow regime. In impermeable ground such as clay, however, the underground built environment such as heated spaces have shown to have a significant impact on improving the geothermal extraction efficiency.

This study aims to estimate geothermal potential, radioactivity levels, and environmental pollution of six most popular spas in Central Serbia (Ovčar, Gornja Trepča, Vrnjačka, Mataruška, Bogutovačka and Sokobanja), as well as to evaluate potential exposure and health risks for living and visiting population. Thermal possibilities of the studied spas showed medium and low geothermal potential with total thermal power of 0.025 MW. Gamma dose rates in air varied from 63 to 178 nSv h-1. Specific activities of natural radionuclides (226Ra, 232Th and 40K) and 137Cs in soil were measured; annual effective doses and excess lifetime cancer risk from radionuclides were calculated. Radon concentration in thermal-mineral waters from the spas ranged between 1.5 and 60.7 Bq L-1 (the highest values were measured in Sokobanja). The annual effective dose from radon due to water ingestion was calculated. The analyzed soils had a clay loam texture. The presence of As, Cr, Cu, Fe, Mn, Ni, Pb, Cd, Zn, and Hg in soil was investigated. The concentrations of As, Cr, Ni, and Hg exceeded the regulatory limits in many samples. Soil samples from Mataruška spa were generally the most contaminated with heavy metals, while the lowest heavy metal concentrations were observed in Sokobanja. Health effects of exposure to heavy metals in soil were estimated by non-carcinogenic risk and carcinogenic risk assessment. Total carcinogenic risk ranged between 6 × 10-4 and 137 × 10-4 for children and between 0.1 × 10-4 and 2.2 × 10-4 for adults. The sum of 16 PAHs analyzed in soil samples varied from 92 to 854 μg kg-1.

In metropolitan areas, shallow groundwater temperatures are affected by anthropogenic heat sources. The resulting thermal conditions in the subsurface are highly site-specific, and spatial and temporal trends have only been revealed for a few cities. In this study, the anthropogenic heat input is quantified for 15 locations in Osaka, Japan using an analytical, one-dimensional conductive heat transport model. Mean anthropogenic fluxes into the subsurface are determined annually between 2003 and 2011. The model depicts fluxes from buildings and from different land cover types separately. The main objective is to compare the predicted annual mean heat input to heat storage increase, and to identify site-specific factors relevant for the thermal evolution of the underground at each well location. Our results indicate that mean fluxes from asphalt covered areas (0.28 ± 0.07 W/m2) and from buildings (0.32 ± 0.18 W/m2) are significantly higher than fluxes from unpaved (0.06 ± 0.06 W/m2) and grass-covered (-0.04 ± 0.06 W/m2) areas. Furthermore, the temporal variation of mean fluxes from buildings is stable over the studied time period, while annual mean fluxes from asphalt, grass and unpaved areas vary as much as 0.8 MJ/m2. Still, the uncertainty associated with the combined annual heat input of all heat sources is slightly higher than the changes between the years. Overall, the predicted cumulative heat input (2003 to 2011) at the wells ranges from 4 MJ/m2 to 60 MJ/m2. Comparing these results to heat storage increase, additional local heat fluxes, such as from construction work or a sewage treatment plant, have to be considered for about 1/3 of the wells. In addition, it becomes apparent that a significant percentage of determined anthropogenic heat input is not stored in the urban aquifer and heat input is predicted to be considerably higher than heat storage increase.

Underground structures have a major influence on groundwater temperature and have a major contribution on the anthropogenic heat fluxes into urban aquifers. Groundwater temperature is crucial for resource management as it can provide operational sustainability indicators for groundwater quality and geothermal energy. Here, a three dimensional heat transport modeling approach was conducted to quantify the thermally affected zone (TAZ, i.e. increase in temperature of more than +0.5°C) caused by two common underground structures: (1) an impervious structure and (2) a draining structure. These design techniques consist in (1) ballasting the underground structure in order to resist hydrostatic pressure, or (2) draining the groundwater under the structure in order to remove the hydrostatic pressure. The volume of the TAZ caused by these underground structures was shown to range from 14 to 20 times the volume of the underground structure. Additionally, the cumulative impact of underground structures was assessed under average thermal conditions at the scale of the greater Lyon area (France). The heat island effect caused by underground structures was highlighted in the business center of the city. Increase in temperature of more than +4.5°C were locally put in evidence. The annual heat flow from underground structures to the urban aquifer was computed deterministically and represents 4.5GW·h. Considering these impacts, the TAZ of deep underground structures should be taken into account in the geothermal potential mapping. Finally, the amount of heat energy provided should be used as an indicator of heating potential in these areas.